Mass Analyzed Threshold Ionization Spectra Of Several Aniline And Benzonitrile Derivatives

The spectrum is the "fingerprint" of atoms and molecules,which can be used to distinguish the type of molecules.The intensity of the spectrum reflects the relative abundance of atoms or molecules.Organic molecules are the foundation of life,and the spectra of many organic molecules have not been reported.In this paper,the vibronic spectra of excited and ionic states of o-aminobenzonitrile,m-aminobenzonitrile,p-isopropylaniline and p-ethoxybenzonitrile were studied by resonance enhanced multiphoton ionization?REMPI?and massanalyzed threshold ionization?MATI?spectroscopy.Gaussian is an importantand widely used quantum chemistry calculation software.In this paper,molecular geometry optimization,energy and vibration frequency were calculated using Gaussian.For the ground state S₀ and the ion ground state D₀,the density functional theory?DFT?calculation of B3PW91/6-311++G?d,p?level was used,and for the excited state S₁,DFT calculation of TD-B3 LYP /6-311++G?d,p?level was used.o-aminobenzonitrile and m-aminobenzonitrile are commonly used as intermediates in synthetic medicine.In this paper,two-color resonance two-photon ionization?R2PI?spectra and mass-analyzed threshold ionization?MATI?spectra of these two molecules were measured,and the S₁?S₀transition energy and precise ionization energy of o-aminobenzonitrile were determined to be 31265 ± 2 cm^-1 and 66653 ± 5 cm^-1,respectively.The S₁?S₀ transition energy and the precise ionization energy of m-aminobenzonitrile were determined to be 31710 ± 2 cm^-1 and 66846 ± 5cm^-1,respectively.The precise ionization energies and ionic vibrational spectra are reported for the first time.The REMPI and MATI spectra were theoretically simulated,and the simulated and measured spectra arein good agreement.According to the theoretical calculations,simulation spectra and the known similar molecular assignment,the measured vibration spectra ofthe excited states and the ionic ground states were assigned.Both p-isopropylaniline and p-ethoxybenzonitrile are commonly used as raw materials for pesticides and pharmaceuticals.The one-color REMPI spectra and the two-color MATI spectra of the two molecules were measured,and the S₁?S₀ transition energy and the precise ionization energy of the p-isopropylaniline were determined to be 33342 ± 2 cm^-1 and 59755 ± 5 cm^-1,respectively;The S₁?S₀ transition energy and precise ionization energy for p-ethoxybenzonitrile were determined to be 35525 ± 2 cm^-1 and 69598 ± 5cm^-1,respectively.The precise ionization energy and the vibrational spectraare reported for the first time.According to the theoretical calculation results,the measured vibration spectra of the excited state and the ion ground state were assigned.